1. Field of the Invention
The present invention relates to a hubcap breather assembly located in a hubcap for an automotive vehicle, particularly a heavy-duty vehicle such as a truck trailer or truck tractor.
2. Description of the Prior Art
The wheel and axle assemblies of certain automotive vehicles, particularly large trailers and semi-trailers and the tractors used to pull them, are formed with wheel hubs having lubricant chambers. The wheel bearing lubricant chambers are located at the outboard ends of the axles and contain the wheel bearings and also a lubricant, such as lubricating oil. The lubricating oil partially fills the lubricant chambers and forms a continuous bath through which the wheel bearings of the wheel pass in rotation as the wheel turns. The wheel bearing lubricant chambers are thereby partially filled with air and partially filled with a lubricating liquid, such as lubricating oil.
During operation of the automotive vehicle the temperature of the wheel bearings rises considerably above ambient atmospheric temperature. During periods of nonoperation of the vehicle the temperature of the wheel bearings falls, and approaches ambient atmospheric temperature when the automotive vehicle remains parked for a considerable period of time. The changes in temperature result in changes in pressure within the wheel bearing lubricant chambers, since the gasses in the atmosphere, primarily nitrogen and oxygen, contract upon cooling and expand upon heating. Therefore, it has long been advisable for the wheel bearing chambers to be vented to atmosphere. This allows pressure within the sealed bearing chambers to equalize with surrounding atmospheric pressure irrespective of the temperature of the lubricant in the lubricant chamber so that the wheel bearing chamber seals do not rupture.
However, the venting of the lubricant chamber to atmosphere creates certain problems. Specifically, as air passes into a bearing lubricant chamber to equalize pressure therewithin when the vehicle is parked or operating at a lower speed, airborne dirt, dust, and water can enter the lubricant chamber. These contaminants become entrapped in the lubricant and cause excessive wear on the wheel bearings and excessively high temperatures in the lubricant chamber when the vehicle is subsequently operated. This leads to a reduction of useful life for the wheel bearings and lubricant seals.
Various systems have been devised to attempt to filter air passing into lubricant chambers that contain lubricant and wheel bearings. Some of these are described, for example, in the following issued United States patents: U.S. Pat. Nos. 5,482,358; 5,664,846; 5,752,746; 5,785,390; and 5,860,708. Each filtration system employed in these prior devices adopts its own particular approach to the problem. However, none of these prior devices has been particularly effective in excluding dust, dirt, water, and other contaminants from the hubcap lubricating chambers in automotive vehicle wheels.